1. Field of The Invention
This invention concerns an improved superregenerative detector that may be used in the radio frequency remote control of appliances, such as ceiling fans, and/or associated lighting, and more particularly, a superregenerative detector including feedback elements within the detector for stabilizing the detector output.
2. Description of Related Art
The remote control of business and home appliances, particularly ceiling fans and companion lighting, has become increasingly more popular. Such features as variable fan speed, fan reversibility, light intensity adjustment, and decorative appearance have made the ceiling fan and companion light a sought after addition to households and work environments. Further, these popular features have been made even more attractive with the advent of controllers that permit the user to vary the fan and light functions at a distance and without the need for manipulating a pull chain or string unattractively hanging from the fan or light.
However, there have been drawbacks associated with certain forms of remote control. For example, remote control by infrared or ultrasound suffer from "line-of-sight" limitation. Particularly, these forms experience signal interruption in the presence of physical obstructions such as walls, floors, etcetera, or even the blades of the fan itself. Additionally, these approaches are susceptible to interference from "noise", e.g., background light and sound, which may cause false control of the system.
On the other hand, however, remote control of appliances such as ceiling fans and associated lighting has been effectively accomplished with radio frequency (r.f.) signals. Physical objects such as walls, floors, and the like, while obstructions to light and sound forms of remote control, are transparent to r.f. signals. Further, an r.f. transmitter can be easily carried and manipulated by hand thereby permitting the operator freedom of use.
While r.f. controllers for combined ceiling fan and lighting fixtures have been known, problems have existed with them. For example, certain designs have been elaborate and complicated raising questions of cost and reliability. In accordance with certain prior designs, pulse counting techniques proposed for processing the control data required use of separate channels and frequencies to manage fan operation and light intensity. Accordingly, this multiplication of channels and frequencies results in an increase in system complexity and duplication of system components. As will be appreciated, increased complexity and component duplication raise cost and reduce reliability; results which are commercially unattractive.
R.f. controllers, however, have been developed which permit control of multiple fan features as well as operation of associated lighting, with a single frequency and channel. MEDCO, Ltd. of Deer Park, N.Y., has offered a fan and light controller of digital designs which features a pulse-width modulation scheme in a single-channel system. The Medco controller permits control of fan activation, speed selection and direction as well as the intensity of associated lighting with a single modulated r.f. carrier signal.
However, even in single-channel systems of the type offered by MEDCO, Ltd., competing design considerations creates difficulties. Particularly, in order to stay price competitive, the system component costs must be kept low. But, where component costs are cut, as for example, by using a low-cost detector such as one of the superregenerative type that employs fewer components that other types such as the superregenerative type, sensitivity is reduced. And, where receiver sensitivity is reduced, system range is, likewise, reduced, with the effect of preventing use of the remote controller where it can be particularly attractive; for example, large rooms or high ceilings commonly found in commercial or industrial buildings, or from adjoining rooms or outside residential structures.
Further, since the sensitivity and reliability of operation of a conventional superregenerative detector depends upon the range of linearity of the active components included in the detector, it is necessary to specially select such active components for required linearity. However, specially selecting active components for linearity increases their costs and prevents realization of the full potential for cost reduction that the reduced component count of a superregenerative detector would otherwise present.